It's difficult to tell from the picture on the page, but the hole in the peep sight itself is adjustable to increase or decrease the aperture
The one in the link appears to be a fixed aperture, you'd have to change out the insert to change the aperture size. It may be possible that an adjustable diopter disc would work in that sight, but I'm not familiar with that sight. You'd have to contact the maker.
I recently put a Centra AR flattop rear sight and Phoenix Precision front sight on my AR. Both have the adjustable iris inserts and can allow you to shoot much more accurately than traditional peep sight...but they did cost a nice chunk of change. I could have bought a very
nice scope instead, but I prefer iron sights even at long distances so for me the money was better spent on nice irons.